Such a CVD reactor is described in JP 2002-146540 A. The substrate holder has a pocket formed by a depression, which has a further depression in its middle zone. The substrate rests on the edge step thus formed, which is raised in relation to the central zone of the base of the pocket. A heater, which is spaced apart from the bottom side of the substrate holder by a gap, is located underneath the substrate holder. The heater consists of multiple circumferential sections, which are spaced apart from one another by depressions. The bottom side of the substrate holder has a depression in a central region lying under a middle zone of the pocket, so that the gap height of the insulation gap is greater there than in a circumferential region surrounding this central region. A central heating element, using which the central region can be heated, lies underneath the central region. Spaced apart therefrom in the radial direction by a gap, a further heating element surrounding the first heating element is located, which can separately heat the surrounding region.
EP 0 160 220 B2 describes a substrate holder, in which the substrates also only rest on one edge of a pocket.
US 2011/0049779 A1 is concerned with the problem that substrates, which are coated in a CVD reactor with different layers at different temperatures, can curve as a result of different properties of the layers. For example, if a layer having a greater coefficient of thermal expansion than the substrate is deposited on the substrate in the coating process and the substrate is brought to a lower temperature or brought to a higher temperature in a following process step, the substrate curves in one direction or the other direction. Since the substrate is only supported on selected support regions and in particular only at the edge and otherwise extends freely over the base of the pocket, it is essentially heated by heat conduction via the gas between substrate and pocket base. In the case of a curve upward, the gas gap enlarges in the middle region, so that less heat is transported to the substrate there, with the consequence that the surface of the substrate has a lower temperature there than in the edge region. This has the consequence that the electrically—or optically—active layers deposited on the substrate have different properties from one another laterally. These inhomogeneities are very disadvantageous in particular in the manufacturing of light-emitting diodes and therein in the manufacturing of MQW (multi-quantum wall).
DE 10 2006 018 514 A1 describes a substrate holder, in which a rotationally-driven carrier, which can respectively carry one or multiple substrates, lies in each of a plurality of pockets. The substrates lie on the top side of the rotatable carrier. The rotatable carrier is mounted on a gas cushion. The gas forming the gas cushion can have various thermal conductivities. A recess is located in the bottom side of the carrier, so that the gas cushion between the base of the pocket and the bottom side of the carrier has zones of various gap heights. By variation of the thermal conductivity of the gas, the temperature profile on the top side of the carrier and therefore the substrate temperature can be locally influenced.